﻿Shader "Custom/Draw"
{
	Properties
	{
		_Point1("Point1",vector) = (100,100,0,0)
		_Point2("Point2",vector) = (200,200,0,0)
		_LP1("linePoint1",vector) = (300,100,0,0)
		_LP2("linePoint2",vector) = (600,400,0,0)
		_LineWidth("LineWidth",range(1,20)) = 2.0

	}

	SubShader
	{
		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
			};

			struct v2f
			{
				float4 vertex : SV_POSITION;
			};
			float4 _Point1;
			float4 _Point2;
			float4 _LP1;
			float4 _LP2;
			float _LineWidth;

			v2f vert(appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				return o;
			}

			fixed4 frag(v2f i) : SV_Target
			{
				//绘制圆形，此处半径使用了固定值1000和500,当然大家也可以把他们写成可调的参数
				if (pow((i.vertex.x - _Point1.x),2) + pow((i.vertex.y - _Point1.y),2) < 1000)
				{
					return fixed4(0,1,0,1);
				}
				if (pow((i.vertex.x - _Point2.x),2) + pow((i.vertex.y - _Point2.y),2) < 500)
				{
					return fixed4(1,0,0,1);
				}

				//绘制直线上两点
				if (pow((i.vertex.x - _LP1.x),2) + pow((i.vertex.y - _LP1.y),2) < 100)
				{
					return fixed4(0,0,1,1);
				}
				if (pow((i.vertex.x - _LP2.x),2) + pow((i.vertex.y - _LP2.y),2) < 100)
				{
					return fixed4(0,0,1,1);
				}

				//计算点到直线的距离
				float d = abs((_LP2.y - _LP1.y)*i.vertex.x + (_LP1.x - _LP2.x)*i.vertex.y + _LP2.x*_LP1.y - _LP2.y*_LP1.x) / sqrt(pow(_LP2.y - _LP1.y,2) + pow(_LP1.x - _LP2.x,2));
				//小于或者等于线宽的一半时，属于直线范围
				if (d <= _LineWidth / 2)
				{
					return fixed4(0.8,0.2,0.5,1);
				}

				//绘制网格直线
				if ((unsigned int)i.vertex.x % (unsigned int)(0.25*_ScreenParams.x) == 0)
				{
					return fixed4(0,0,1,1);
				}
				if ((unsigned int)i.vertex.y % (unsigned int)(0.1*_ScreenParams.x) == 0)
				{
					return fixed4(0,0,1,1);
				}
				//默认返回白色
				return fixed4(1,1,1,1);

			}
			ENDCG
		}
	}
}